What did we do?


Today, we went to the STM. After the bakeout, the STM is degassing, which means that the different parts of the apparatus are heating in order to get rid of contaminants. For instance, some filaments are heated, to clean the layout.

Then, the researchers will have to cool the apparatus and prepare the samples. There are two chambers separated.

During the degassing, the pressure increases because there are more contaminants in the layout (which will be eliminated). That's why there is a peak of pressure during the degassing. For the experiments, the pressure has to be near 10-11mb.




Then we went to the other STM in order to see the filling of the cryostat: the STM is composed of a cryostat which cools the vacuum chamber thanks to liquid azote and liquid helium. The sample and the tip are inside this vacuum chamber. Liquid azote can be introduced in the apparatus easily, whereas it is harder with liquid helium: gas helium is first introduced in the cryostat in order to get atmospheric pressure, and then it is possible to introduce liquid helium.

Liquid azote carboy

Liquid helium carboy


We also began to make the tips which will be used for the STM experiments. These particular tips are threads in platinum (near 80%) and iridium, because they are relatively inert. They have to be cut, cleaned, and we have to weld them on the bracket which will be put in the STM. Tomorrow, we will cut the threads in order to get a tip.


The threads cutting


The threads and their brackets


The threads welding